1. Field of the Invention
The present invention relates to optical switches used in fiber communication and optical network technology, and particularly to a mechanical optical switch with a prism as a switch element.
2. Description of Prior Art
For purposes of convenience and economy, it is often desirable to employ switches in optical networks, so that either a single optical signal can be shared between two or more users or a single user can choose from a variety of optical signals without the added expense and complexity of installing additional hardware.
Optical switches can be classified as mechanical optical switches or as non-mechanical optical switches. Mechanical optical switches realize changes in lightpaths by moving optical fibers or elements using principles of mechanics or electromagnetism.
Referring to FIGS. 9A and 9B, U.S. Pat. No. 6,154,586 discloses an optical switch 99 which, in a first state, reflects an input light beam from an input port 82 to a reflection output port 83, and in a second state, transmits an input light beam from the input port 82 to a transmission output port 84. The optical switch 99 further comprises a block 81 made of a light transparent substrate, which has a reflective surface 811. A reflective cavity 86 and a transmissive cavity 87 are defined in the block 81, and are spaced by a light transparent diaphragm 85. The reflective cavity 86 and the transmissive cavity 87 are respectively filled with a reflective and transmissive fluid. The optical switch 99 further comprises an actuator 7 connected with the transmissive cavity 87 by a connecting channel 71. The actuator 7 controls the light transparent diaphragm 85 contacting with or detaching from the reflective surface 811.
Referring to FIG. 9A, the optical switch 99 is at the first state, and the reflective fluid covers the reflective surface 811 of the block 81. The input light beam from the input port 82 is incident on the reflective surface 811 at an angle which is equal to or greater than a critical angle determined by the refractive indices of the reflective surface 811 and the reflective fluid of the reflective cavity 86. The light beam is totally reflected to the reflection output port 83. Referring to FIG. 9B, the optical switch 99 is at the second state, and the transparent diaphragm 85 contacts with the reflective surface 811. The input light beam from the input port 82 is incident on the reflective surface 811 at an angle which is smaller than a critical angle determined by the refractive indices of the reflective surface 811 and the transparent diaphragm 85. The light beam is transmitted to the transmission output port 84 through the block 81.
However, the optical switch above mentioned has some shortcomings. First, the reflective cavity 86 and the transmissive cavity 87 of the block 81 are filled with fluid. In order to prevent fluid from leaking out of the cavities 86, 87, the block 81 must have good seals, thus increasing the cost of the optical switch. Second, when the transparent diaphragm 85 contacts with the reflective surface 811, residual fluid is unavoidably left between the transparent diaphragm 85 and the reflective surface 811, thus reducing performance of the optical switch.
An improved optical switch having good performance and low cost is desired.
Accordingly, an object of the present invention is to provide an optical switch having good performance and low cost.
To achieve the above objects, an optical switch in accordance with the present invention comprises an input device, a reflection output device, a transmission output device, a prism and a rotation device. The input and reflection output devices are rotatable around the prism between a first position and a second position. The prism has a reflective surface to effect optical switching. When the input and reflection output devices are at a first position, an input light beam from the input device passes through the reflective surface of the prism, and is output through the transmission output device. When the input and reflection output devices are at a second position, the input light beam from the input device is incident on the reflective surface of the prism at an angle which is equal to or larger than a critical angle of the prism. The input light beam is totally reflected by the reflective surface of the prism, and is output through the reflection output device.